Masking agent for middle distillates



United States Patent 3,156,542 MASKHNG AGENT FOR DLE DISTILLATEd Edwin C. Yonnghouse, Cranford, N.J., assiguor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Feb. 16, 1961, Ser. No. 89,645 2 (Ilaims. (Cl. 4459) The present invention is concerned with improved fuels with respect to exhaust odor characteristics boiling in the range from about 250 to 750 F. More particularly the invention relates to improved diesel fuel compositions wherein the diesel fuel contains an odor masking agent so as to mitigate the obnoxiousness of exhaust fumes from diesel engines. The composition, in accordance with the present invention, comprises a middle distillate fuel in combination with a masking composition comprising vanillin, preferably in combination with musk xylene. A preferred masking composition comprises oxo bottoms in combination with vanillin and musk xylene. It is well known in the art to burn middle distillate fuels under various conditions. It is known, for example, to burn diesel fuels in diesel engines wherein the odors evolved are ill-smelling and abnoxious. In accordance with the present invention, a composition is utilized comprising a middle distillate having in combination therewith a masking formulation comprising musk xylene in combination with vanillin. It is preferred that the masking composition comprise vanillin, oxo bottoms and musk xylene. Other compositions are suggested such as musk xylene in combination with a dicarboxylic ester; musk xylene in combination with tertiary butyl phenol; musk ambrette and musk xylene.

It is therefore the principal object of the present invention to set forth an improved masking agent for middle distillates, particularly for diesel fuels. The boiling ranges of these fuels are generally from about 250 to 750 F.

The petroleum distillate fuels in which the additive materials of the invention are employed consist of a major proportion, at least 95%, of liquid hydrocarbons boiling at temperatures between about 100 F. and about 750 F. These fuels include aviation turbine engine fuels such as JP-l, JP4 and lP-S fuels, and diesel fuels such as marine, stationary and automotive diesel engine fuels.

Aviation turbine engine fuels consist of at least 95% of a mixture of volatile hydrocarbons. It is defined by US. Military Specifications MlLF-56l6 and MIL-F- 5624C. its volatility is such that its end point does not exceed 572 F. Its viscosity is between 0.5 and 1.5 centistokes at 100 F.

Diesel fuels as referred to in connection with the invention consist of at least 95% of a mixture of hydrocarbons boiling between 250 F. and 750 F. either by ASTM Method D-86-56 when their end points do not exceed 600 F. or by ASTM Method Dl58-54. Diesel fuels are defined by ASTM Specification D-97553T and fall into Grades 1D, 2D and 4D, in all of which the additive materials of the invention may be used. They have viscosities between 1.4 and 26.4 centistokes.

The liquid fuels in which the additive materials may be incorporated thus comprise at least 95% by weight of a mixture of hydrocarbons having a boiling range between the limits of 100 Rand 750 F. and a viscosity between the limits of 0.5 and 26.4 centistokes. at 100 F.

One ingredient of the masking composition of the present invention comprises vanillin CH0 1 OOCH J used in an efi'ective amount with musk xylene. It has been found that when vanillin is used in combination with musk xylene and a particular liquid synthesis product derived from the reaction between olefins, carbon monoxide and hydrogen, the latter known as oxo bottoms, an ideal composition i secured to overcome or mitigate the obnoxiousness of exhaust fumes from diesel engines.

The oxo bottoms product is produced by what is now the well known two-stage process for producing oxo alcohols (see e.g. US. Patent 2,327,066). In the first stage an olefinic material, a carbonylation catalyst, and CO and H are reacted to give a product which consists predominantly of aldehydes. This material is catalytically hydrogenated in the second stage to give the corresponding alcohols. The overall reaction may be formulated as follows:

Both the aldehyde and the alcohol formed as a result of the reaction contain one more carbon atom than the olefinic material from which they are derived.

The carbonylation, or oxo stage, as it is sometimes called, is widely useful and is used effectively with both long and short chain olefinic compounds, depending on the type alcohol desired. Thus, straight and branch chained olefins and diolefins such as propylene, butylene, butadiene, pentene, pentadiene, hexene, heptene, olefin polymers such as diand tri-isobutylene, the hexene and heptene dimers, polypropylenes, and olefinic fractions from the hydrocarbon synthesis process or from thermal or catalytic cracking operations, and other sources of hydrocarbon fractions containing such olefins may be used as starting materials, depending on the nature of the final product desired. In general, olefins having up to about 18-20 carbon atoms in the molecule are preferred in this reaction. Olefins of C to C ranges are, of course, required to prepare the commercially preferred C to C16 alcOhOlS.

The catalystsfor the first stage of the process are usually employed in the form of the catalytically active metal salts of high molecular weight fatty acids such as stearic, palmitic, or oleic, naphthenic acids and similar acids. Thus, examples of suitable catalysts are such organic salts as cobalt stearate, oleate, or naphthenate or iron linoleate. These salts are soluble in the liquid olefin feed and may be supplied to the first reaction zone as hydrocarbon solutions, preferably dissolved in the olefin feed.

The synthesis gas mixture fed to the first stage may consist of any ratio of H to CO, but preferably these two gases are present at about one volume hydrogen per volume of CO. The conditions for the reaction of olefins with H and CO Vary somewhat in accordance-with the 3,1 U nature of the olefin feed, but the reaction is generally conducted at pressures in the range of about 1500 to 4500 p.s.i.g., and at temperatures in the range of about 150 to 450 F.

The hydrogenation stage may be operated at conventional hydrogenation conditions which include temperatures, pressure gas and liquid feed rates approximately within the ranges specified above for the first stage. Various known types of hydrogenation catalysts such as nickel, tungsten, molybdenum, their oxides and sulfides and others may be used. These include catalysts of both the sulfur sensitive and sulfur insensitive types. The catalyst may be supported on some suitable carrier such as charcoal. The liquid product from the hydrogenation stage is worked up by distillation to separate the desired alcohols from unconverted olefinic feed material, unhydrogenated carbonyl compounds, and saturated hydrocarbons formed in the process.

In the hydrogenation stage, in the presence of the hydrogenation catalysts and under the conditions employed, further condensations and reactions of the initially formed aldehydes and alcohols take place to give additional high boiling impurities which are generally allowed to remain as the bottoms after the distillation of the main portion of the alcohol is completed.

In a process for the manufacture of iso-octyl alcohol by a two-stage x0 process using a predominantly C olefinic feed, the final distillation of the crude C alcohol product results in a bottoms fraction representing about 30% of the crude alcohol charge to the distillation zone. This bottoms fraction consists of C and some C alcohols, as well as (D -C alcohols, C acetals and C ethers. 01; these constituents, the C alcohols represent the final traces (1-5 remaining in the bottoms from the distillation of the main product. The remaining so-called bottoms consists primarily of higher boiling oxygenated compounds formed by side reactions as outlined above occurring in either the first or second stage of the C alcohol process. As clearly as can be determined by chemical analysis and infra-red absorption spectrographic study, these constituents were identified as C secondary alcohols, C aldehydes or ketones, C acetals, C esters of C naphthenic acids used in making the cobalt catalyst for the first or oxonation stage, and saturated and unsaturated C ethers. A typical chemical analysis of the higher boiling oxygenated compounds obtained in a plant, and free from C -C alcohols fraction, is shown in Table I. The hydroxyl numher, free and combined carbonyl numbers, and saponification and acid numbers are expressed in terms of milligrams of potassium hydroxide per gram of sample analyzed.

TABLE I Typical Composition of the 0x0 Alcohol Bottoms Analysis:

Hydroxyl No. 95

'Free carbonyl N0. 0.5

Combined carbonyl No. 29

Saponification No. 21

Gravity, API 33.3

Acid N0. 0.2

Constituents, percent by wt.:

C15-c1 alcohol C -C aldehyde or ketone 0.2

C acetal 19.1

C (octyl naphthenate ester) -14.7

Saturated C ether (dioctyl ether) 1 17.4

1 Calculated by difference.

Analytical results obtained by chemical and infra-red methods appear to be in essentially good agreement as indicated by their comparison in Table ll below:

Thus, it can readily be seen that the synthetic oxo processes give complex mixtures of compounds having various carbon structures in the molecules and having varied molecular weights. (As to the complex nature of these products see United States Bureau of Mines Publication, R1. 4270 Critical Review of Chemistry of Oxo Synthesis, etc, June 1948.)

The bottoms product from the C olefin feed substantially free of C alcohols, boils in the range of about C. to about 18 weight percent, boiling above 395 C.

It is to be understood that whenever the term 0x0 Bottoms is used in the specification, it indicates a still bottoms product produced by the indicated two-stage operation.

The musk xylene is a compound having the following structural formula:

-CHa

2 4 fi-trinitro-l 3-dirnethyl-5-tertiary butyl benzene This compound can be prepared by nitrating m-tertiarybutyl-xylene.

When utilizing the musk xylene in combination with vanillin alone, it is preferred to use from about 0.001 wt. percent to 0.5 wt. percent of musk xylene and about 0.0002 wt. percent to 0.2 wt. percent of the vanillin bmcd upon the weight of the base fuel. A preferred amount is 0.005% of musk xylene and 0.001% of the vanillin.

When considering the musk xylene in combination with the oxo bottoms and vanillin, it is preferred to use 0.0002 wt. percent to 0.2 wt. percent of the vanillin, 0.0005 wt. percent to 0.05 wt. percent of the musk xylene and 0.005 wt. percent to 0.5 wt. percent of the oxo bottoms. A very desirable combination comprises 0.0005% vanillin, 0.0025% musk xylene, and 0.015% oxo bottoms based upon the weight of the base fuel.

A number of tests were carried out wherein an odor triangulation test was used.

Exhaust odor studies to evaluate the effectiveness of these agents were carried out in a four cylinder GMD engine, Model No. 41715. This engine was equipped to burn two fuels simultaneously, one fuel in cylinders No. 1 and 2 and the other in cylinders No. 3 and 4. Also the exhaust pipes from each set of cylinders were separated to allow the fumes to be sampled independently. In this manner, the exhaust odor from the base fuel (Commercial Diesel Fuel) could be compared directly with exhaust odor from the base fuel treated with the masking agent.

In order to reduce the chances of correct guesses by the odor panelists, an odor triangulation test method was applied. Each panelist sniffed three samples of the exhaust fumes, but two samples were from the same source (pair of cylinders). The panelist was asked first to select the exhaust sample which had a different odor (a no difference choice was also possible). If he found one odor to be different he was asked if he preferred it to the other two. .e preference ratio refers to the number of panelists who preferred the odor from the treated fuel to the total number of panelists who took the test (whether or not they found the correct odor difference).

In most evaluations of the odor masking additives, the treated fuel was first compared with the base fuel in one pair of cylinders Nos. 1 and 2). Later the treated fuel was switched over to cylinders No. 3 and 4 and again compared with the base fuel run in the other pair of cylinders. This procedure minimized the cylinder to cylinder differences in exhaust odors.

The results of these tests are as follows:

EXANIPLE (1) Odor triangulation test comparing 0.02% vanillin in Diesel fuel (kerosene) with the kerosene alone. Eight (8) of 9 odor panelists selected the vanillin treated fuel in preference to the base kerosene fuel.

(2) Odor triangulation test, compare .001% vanillin in kerosene with base kerosene. Five (5) of 9 panelists selected and preferred odor from vanillin treated fuel.

(3) Odor triangulation test, compare .001% vanillin in kerosene with base kerosene. Six (6) of panelists selected and preferred odor from vanillin treated fuel.

(4) Odor triangulation test comparing blend of (001% vanillin/ .005 musk xylene) in kerosene with kerosene alone. Nine (9) of ten odor panelists selected and preferred odor from treated fuel to base fuel odor.

(5) Odor triangulation tests comparing blend of (.0005% vanillin/.0025% musk xylene/015% oxo bottoms) in kerosene with kerosene alone.

Nineteen (19) of 20 odor panelists selected and preferred the odor from the treated fuel to that from base fuel.

The odor masking additive consisting of 0.0005 vanillin, 0.0025% musk xylene and 0.015 oxo bottoms was evaluated further in a series of tests using two diesel city buses. Odor sniff chambers were installed inside of each bus and the flow of exhaust gases regulated to these boxes at the same rate in each coach. Panelists sampled the odor at each operating condition in one bus and then quickly transferred to the other bus for a comparison between the exhaust odors. One bus operated on the base kerosene fuel and the other on the treated fuel (containing 0.0005% vanillin, 0.0025% musk xylene, and 0.015% oxo bottoms). The fuels were also switched between buses 6 and the evaluations repeated. The odor preference ratios from these tests are summarized below.

Preference ratio, No. preferred Operating condition: treated fuel to total samples The bus to bus differences were negligible.

What is claimed is:

1. Diesel fuel composition of improved exhaust odor qualities which consists essentially of a hydrocarbon distillate boiling in the range from 250 F. to 750 F., from about 0.001 wt. percent to 0.5 wt. percent of musk xylene, from about 0.0002 wt. percent to 0.2 Wt. percent of vanillin based upon the Weight of the base fuel and about 0.0115 wt. percent of oxo bottoms based upon the base fue 2. Composition as defined by claim 1 wherein the amount of musk xylene present is about 0.0025 wt. percent and the amount of vanillin present is about 0.0005 Wt. percent.

References Cited in the file of this patent UNITED STATES PATENTS 2,955,928 Smith et a1. Oct. 11, 1960 FOREIGN PATENTS 570,539 France May 15, 1924 670,048 France Aug. 12, 1929 596,535 Germany May 4, 1934 596,536 Germany May 5, 1934 111,661 Great Britain Nov. 7, 1917 359,590 Great Britain Oct. 29, 1931 404,046 Great Britain Jan. 11, 1934 490,201 Italy Feb. 6, 1954 OTHER REFERENCES The Condensed Chemical Dictionary, fifth edition, 1956, Reinhold Pub. Corp., page 1146. 

1. DIESEL FUEL COMPOSITION OF IMPROVED EXHAUST ODOR QUALITIES WHICH CONSISTS ESSENTIALLY OF A HYDROCARBON DISTILLATE BOILING IN THE RANGE FROM 250*F. TO 750*F., FROM ABOUT 0.001 WT. PERCENT TO 0.5 WT PERCENT OF MUSK XYLENE, FROM ABOUT 0.0002 WT. PERCENT TO 0.2 WT. PERCENT OF VANILLIN BASED UPON THE WEIGHT OF THE BASE FUEL AND ABOUT 0.015 WT. PERCENT OF OXO BOTTOMS BASED UPON THE BASE FUEL. 